Heroes and Demons: A photonic life form takes up residence on the holodeck.

Torres beams some "photonic matter" into containment fields, and Janeway attempts to contact Harry to get him to help Torres analyse it, and discovers he's no longer on board the ship. Tuvok tries to scan the holodeck where he's supposed to be, but finds there's interference.

Holodeck malfunction episode GO!

Chakotay and Tuvok, unable to shut down the holodeck (of course), venture in. It's a program based on Beowulf, and probably isn't as good as the movie. They're confronted by Freya, and Chakotay bluffs that they're kinsmen of Beowulf - Harry Kim - who she says is dead. She takes them to the King, who appears to be having a feast. Kim's been killed in combat with the monster, Grendal. However, when they ask to see Grendal, the King tells them to piss off. After a bit of posing, Chaks and Tuvok volunteer to stand watch overnight.

They contact Janeway, who gurns a bit and tells them to see if they can fix the holodeck controls and shut the program down. Also, Janeway and Torres find that there appears to be photonic energy in the holodeck systems, and they speculate that Kim's been turned into energy.

Janeway, Torres and Paris have a mini-meeting and decide to send in the HoloDoc, who doesn't look exactly enthusiastic. Kes gives him a pep talk, as he's obviously worried about the mission.

Paris transfers him onto the Holodeck, and he encounters Freya and introduces himself as Dr Schweitzer. Repeated dialogue a go go. HoloDoc fights one of the King's men and demonstrates how he can let weapons pass right through him, which impresses the Danes no end.

They have another feast, and HoloDoc tells a story about how he inoculated the crew against some measles, which... doesn't really impress anyone. Later on he talks to Freya, who appears to be wearing a surprising amount of makeup for a 6th century Dane, and she snogs him and offers him sex. Sadly, before he's able to take her up on her offer, Grendal shows up and attacks him. He arrives back in sickbay minus his right arm.

After analysis of the readings from the tricorder, Janeway and Torres find evidence of synaptic patterns. When Torres replicates the effect in one of their samples, it breaks out of the containment field, and nips around inside the ship, and they realise that the photonic energy is intelligent. Janeway thinks the three missing crew members are still alive in some lattice or whatever outside the ship. She theories that the others have been taken hostage to get the return of the photonic energy life forms.

HoloDoc returns to the holodeck with the other life form in a containment tube, and is confronted by the warrior he showed up earlier on. After a fight, Freya is stabbed while defending the HoloDoc and dies. HoloDoc continues to the castle and returns the smaller life form to Grendal, which returns Chakotay, Tuvok and Kim.

During the debriefing, HoloDoc says he's decided against using the name Schweitzer.